In this study, we have produced soluble versions of Env glycoproteins derived from a primary isolate stabilized by Phe 43 pocket filling mutations and inter-domain cysteine bonds. We have tested these glycoproteins for immunogenicity in rabbits as a prime for soluble gp140 molecule boost. Breadth of neutralization indicate that these glycoproteins significantly increase neutralization breadth as a prime for the soluble gp140 trimer boosts and both are interesting platforms for further modification to better elicit broadly neutralizing antibodies.